There have been known construction machines such as hydraulic shovels each including an engine and an engine room for housing the engine, wherein the engine room houses a cooled object such as a heat exchanger and a cooling fan producing cooling air flow for cooling the cooled object. These construction machines include one having an exhaust duct formed in an external wall configuring the engine room, such as an engine guard or engine hood (also called “bonnet”) enclosing the internal space of the engine room, wherein the air produced by the cooling fan to cool the cooled object is discharged to the outside of the engine room through the exhaust duct. The exhaust duct has a function of enabling the air in the engine room to be discharged while suppressing leakage of the noise of the engine room to the outside by the shape of a channel formed by the exhaust duct or a sound absorption member provided on an inner surface of the exhaust duct.
For example, FIG. 12 of Japanese Unexamined Patent Publication No. 2001-193102 shows a construction machine including an engine, an engine room for housing the engine, and a cooling fan for producing cooling air flow in the engine room, wherein an exhaust duct extending horizontally along an axial direction of the engine is formed in an upper portion of the engine room, allowing the air of the engine room to be discharged horizontally to the outside of the engine room through the exhaust duct and an air outlet formed at the terminal end of the exhaust duct.
Thus configured construction machine formed with an exhaust duct and an air outlet in an upper portion of an engine room, however, may involve a problem that the components located in the vicinity of the air outlet, such as other devices and structures, inhibit smooth discharge of the air through the air outlet. For instance, a construction machine including an exhaust gas treatment device for purifying the exhaust gas discharged from the engine housed in the engine room may require the exhaust gas treatment device to be placed near the air outlet so as to protrude significantly upward beyond the engine hood, thus preventing the air from being smooth discharged from the air outlet.
In order to allow the air from being smooth discharged through the air outlet regardless of the presence of the exhaust gas treatment device and the like in the vicinity of the air outlet of the exhaust duct, the entire exhaust duct including the air outlet has to have a shape protruding upward beyond the upper end of the exhaust gas treatment device or the like. Establishing this shape, however, requires an increased height of the exhaust duct and further an increased height of the entire engine room, which is not preferable. In other words, it is difficult to allow the air to be smooth discharged through the air outlet of the exhaust duct while giving the engine room a restrained entire height.
Meanwhile, the exhaust duct is required to have an exhaust flow path with large area. It is, however, not preferable to simply enlarge the area of the flow path of the exhaust duct, which deteriorates the noise suppression effect.